1. Field of the Invention
The present invention relates to a web feed method and feed apparatus used in a printing machine.
2. Description of Related Art
A conventional web feed apparatus will be described with reference to FIG. 13 to FIG. 18.
FIG. 13 is a schematic drawing representing a continuous web feed apparatus 1a wherein a web 3 is attached to the tip of a new web roll 2b at zero speed when the amount of the web remaining on the web roll 2a feeding a running web 3 becomes small. FIGS. 14 and 15 are schematic drawings representing a continuous web feed apparatus 1b using a rotary arm 56 wherein web 3 is attached while the web 3 being fed is running. FIG. 16 shows an example of the shaft end of a support shaft 57 mounted on a web feed apparatus 1 using a rotating arm (R) 56 when electricity or fluid is supplied. FIG. 16(a) indicates the case where electricity is used, while FIG. 16(b) indicates the case where fluid such as compressed air or pressurized water is used. FIG. 17 is a schematic drawing representing a continuous web feed apparatus Ic, wherein the new web is attached to the web 3 while it is running, and the support shaft 57 of the rotary arm 56 supporting the web roll 2 does not penetrate the rotational center. FIG. 18 is a schematic drawing representing a continuous web feed apparatus Id in which web attachment is performed while the web 3 is running, and a rocking arm 59 (S) that does not rotate is used.
FIGS. 13(a) and (b) are schematic drawings showing a continuous web feed apparatus 1a in which the web 3 is attached at zero speed. The web 3 fed from the web roll 2a passes through an upper guide roll group 51 and a lower guide roll group 52 alternately, and is fed to the next apparatus over a long-distance route.
In the status shown in FIG. 13(a), when the amount of the web remaining on the web roll 2a becomes small and the roll 2a is to be switched over to a new web roll 2b, the web 3 stored in a web storage apparatus 50 is discharged by reducing the gap H between the upper guide rolls 51 and the lower guide rolls 52 as shown in FIG. 13(b). Then, web roll 2a is stopped and an automatic web connecting apparatus 30 is operated; then the running web 3 is pressed against the tip of a new web roll 2b by a pressing apparatus 37. When the web 3 on the side of the web roll 2a is cut off by a saw blade 38, the web 3 can be fed from the new web roll 2b. After that, the web storage apparatus 50 is returned to the original position (as shown in FIG. 13(a)) with the speed of web roll 2b being increased, and the web 3 is thus continuously fed. The amount of stored web is then brought to a maximum to become ready for the next attachment of a subsequent roll web.
Further, FIG. 14 shows the configuration in which attachment is carried out with the web 3 kept running, and the front and back surfaces of the web 3 to be fed are kept unchanged. The web attachment procedure can be briefly described as follows: Web 3 is supplied from the web roll 2a as shown in FIG. 14(a). When the amount of the web remaining on the web roll 2a becomes small as shown in FIG. 14(b), the new web roll 2b is driven so that its surface speed will be the same as that of running web 3. An automatic web attachment apparatus 30 is actuated and the running web 3 is pressed against the new web roll 2b by the pressing apparatus 37. After the running web 3 has been attached to the tip of the web on the new web roll 2b, the web 3 having been fed from the web roll 2a is cut off by the saw blade 38, and the web 3 then comes from new web roll 2b. 
In the state shown in FIG. 14(c), a remaining web core 6 is removed by an unloading apparatus (not illustrated). As shown in FIG. 14(d), a new web roll 2a′ ready for attachment at the tip of the web is mounted by a loading apparatus (not illustrated), and the arm 56 supporting the web rolls 2 is turned in the direction indicated by an arrow in the drawing so that the condition shown in FIG. 14(b) is realized. This procedure is repeated to feed the web 3 continuously. When a high-quality web is to be fed, a problem may occur if front and back sides are reversed by the splicing of web 3. This arrangement is preferable in the sense that such a problem can be avoided. In FIG. 14, a support shaft 57 supports the arm 56, and in FIG. 15, an arm rotating apparatus 58 is mounted on a frame 4.
A continuous web feed apparatus Ic in FIG. 17 has the same basic functions as those of the continuous web feed apparatus 1b given in FIGS. 14 and 15, the difference being found in the structure of the support shaft 57 and the overall size of the continuous web feed apparatus 1. Namely, in the continuous web feed apparatus 1b shown in FIGS. 14 and 15, the support shaft 57 penetrates across the width. Assume that the maximum diameter of web rolls 2 is “D”, the diameter of the support shaft 57 at the center is “d”, and the required minimum clearance is “C”. Thus, one finds the maximum overall rotating dimension K to be given by K=2D+d+C. In the continuous web feed apparatus Ic shown in FIG. 17, on the other hand, the support shaft 57 is provided only on the outside with respect to the arms 56 located on the opposite sides across the width of web rolls 2, without any support shaft mounted inside (on the side of the web rolls). Beams 13 are installed separately. Thus, the maximum overall rotating dimension K equals 2D+C.
FIGS. 18(a) and (b) show a continuous web feed apparatus Id wherein the arm 59 supporting the web roll 2 feeds the web 3 continuously by rocking, not by rotation. This continuous web feed apparatus Id comprises (1) arms 59a and 59b supporting two web rolls 2a and 2b, respectively, (2) an automatic web splicing apparatus 30a for splicing the web 3a on the left to the new web roll 2b, and (3) an automatic web splicing apparatus 30b for splicing the web 3b on the right to the new web roll 2b. The arms 59a and 59b are supported by support shafts 60a and 60b, and are designed to rock about the support shafts 60a and 60b. 
FIG. 18(a) shows how web 3 is unwound from the web roll 2a. When the amount of the web remaining on the web roll 2a becomes small, the surface speed of new web roll 2b is increased to reach the same speed as that of the running web 3a. The automatic web splicing apparatus 30a is pushed out in the arrow-marked direction, and the web 3a is pressed against the new web roll 2b by the pressing apparatus 37a. The web 3a is brought in contact with the tip of the web on the web roll 2b, and web 3b is unwound from the web roll 2b. At the same time, the web 3a having been unwound from the web roll 2a is cut off by the saw blade 38a. Then the web core remaining on the web roll 2a is removed by the unloading apparatus (not illustrated), and a new web roll 2a′ is installed by the loading apparatus (not illustrated) as shown in FIG. 18(b). Further, when the amount of the web remaining on the web roll 2b becomes small, the surface speed of new web roll 2a′ is increased to reach the same speed as that of the running web 3b. The automatic web splicing apparatus 30b is moved in the arrow-marked direction, and the web 3b is pressed against the new web roll 2a′. Then the web is spliced and switched in the same procedure as above.
In the aforementioned prior art web feed apparatus and feed method, however, a continuous web feed apparatus 1a shown in FIG. 13 requires that the dimensions of the web storage apparatus 50 represented by dimensions L and H shown in FIG. 13(a) be large in order to compensate for the time required in web splicing and switching by the amount of the stored web when the machine speed is increased. This, in turn, requires that the installation space be increased as the speed increases. Moreover, a required installation space is increasing due to the recent trend of increasing machine speeds.
Further, the continuous web feed apparatus 1b of rotary arm type shown in FIGS. 14 and 15 is equipped with many devices operated by electric and hydraulic means, such as (1) a device for moving the arm 56 to mount the web roll 2 on this arm 56 or moving the chuck supporting the core of the web roll 2, (2) a brake device for giving an appropriate tension to the web roll 2 unwinding the web 3, and (3) a driving device for acceleration of the new web roll 2. When electricity or fluid is supplied to the side of the rotating arm 56 from the power supply or fluid source provided on the stationary side (frame 4., etc.), a special apparatus as shown in FIG. 16 is required.
FIG. 16(a) shows a slip ring 53 as an example of the apparatus for transmitting electricity from the stationary side to the rotary side. This slip ring 53 is provided on the rotating support shaft 57 according to each type of electricity (having different signal, voltage, etc.) to be connected. It slides in contact with carbon, etc., whereby electricity is transmitted from the stationary side. However, it has a complicated structure and involves complicated procedures in the replacement of consumed carbon or in the maintenance work to keep the surface conductivity of the slip ring 53 in good conditions. This requires a great deal of time and costs. Further, it is difficult to maintain high performances of a high-precision control system 4 when the slip ring 53 is used, because of many problems; namely, insulation work is essential for a large capacity product, for example. Further, the installation space must be expanded.
FIG. 16(b) shows a rotary joint 54 as an example of the apparatus which feeds fluid from the stationary side to the rotating side. In this rotary joint 54, the pipe on the stationary side and individual flow paths provided on the rotating support shaft 57 are connected with each other. In this case, a clearance for rotation is required between the rotary portion and stationary portion. Presence of a clearance is accompanied by possible fluid leakage. So sealing material 55 for avoiding fluid leakage is necessary. However, sealing material 55 is a consumable component which requires maintenance work. At the same time, this increases rotational loads. Moreover, many flow paths requiring difficult machining work is required inside the support shaft 57; and this will increase costs. Further, similarly to the case of the aforementioned slip ring 53, the overall installation space must be increased since rotary joint 54 is provided.
In the continuous web feed apparatus Ic shown in FIG. 17, an improvement is found in the sense that the installation space is reduced; however, it still requires installation of the slip ring 53 for feeding the web 3 continuously by rotating the support shaft 57 mentioned in the description made with reference to FIGS. 14 and 15, and the installation of the rotary joint 54. Alternatively, when they are not installed, complete mechanical means must be used or power must be given from the outside so that the apparatus can be used within a limited space. These problems still remain to be solved.
In the continuous web feed apparatus Id shown in FIG. 18, the arm 59 rocks without rotating when the web roll 2 is switched. This eliminates the need of using the slip ring 53 or rotary joint 54 and provides a simplified structure, but the front and back of the running web 3 are reversed every time the web 3 is spliced and switched. This gives rise to a big problem depending on products in subsequent steps. For example, this will cause subtle differences on the front and back in the case of high quality printing. Moreover, two automatic web splicing apparatuses 30 must be installed, and this creates a problem of increased equipment costs.